True to its word, POF has the highest number of users in this list. The site has 40 million users (fish). You get the full package for free but like other free sites, there are a plethora of premium packages that you can buy such as seeing when other users read your messages. POF was among the first online dating sites and as such, they have been able to refine the site to up user experience. Currently, POF is the fourth most visited dating site in the world.